Rep. Connie Mack IV (R) has hired veteran Washington, D.C., fundraisers in an effort to bolster his Senate prospects, hoping to capitalize on recent polls that have shown him running competitive with Sen. Bill Nelson (D).

According to Republican sources, Mack, at the urging of the National Republican Senatorial Committee, has hired well-known fundraiser Jim McCray to handle his national fundraising and has brought on Michael Gula and Jonathan Graham of Gula Graham to handle his political action committee fundraising. Among its other Congressional clients, the Gula Graham Group has long been been retained by Sen. Jim DeMint (R-S.C.) to run his PAC fundraising. McCray, meanwhile, has worked on multiple GOP presidential campaigns.

Mack, whose father and namesake served in the Senate from 1989 to 2001, is the presumptive GOP nominee against Nelson, whom the NRSC sees as vulnerable even though a competitive statewide race in Florida is expected to cost the party millions.

Roll Call rates the Florida Senate race as Leans Democratic, and most GOP operatives view this contest as an uphill climb. Even Senate Minority Leader Mitch McConnell (R-Ky.) has declined to put this race in his top tier of pick-up opportunities. But the NRSC has been encouraged by the recent polling. As of this morning, Nelson led Mack by 5 points in the RealClearPolitics.com average.

"This is very much a winnable race but it requires all hands on deck for the next three-and-a-half months," a senior GOP strategist who works on Senate campaigns said.